Exposure to Flame Retardant Chemicals and the Occurrence and Severity of Papillary Thyroid Cancer: A Case-Control Study

Presentation Number: SAT 248
Date of Presentation: April 1st, 2017

Julie Ann Sosa*, Kate Hoffman, Amelia Lorenzo, Craig M Butt and Heather Stapleton
Duke University, Durham, NC

Abstract

Background: Papillary thyroid cancer (PTC) is the fastest increasing cancer in the U.S., and data suggest environmental factors, in part, may be responsible. Exposure to flame retardant chemicals (FRs) also has increased over the same time frame; given their thyroid disrupting potential, concern has been raised about their role in the epidemic of PTC.  

Objective: We have evaluated relationships between exposure to a broad range of commonly used FRs and PTC occurrence and severity.

Methods: In a case-control study, we have recruited 140 participants (70 PTC cases and 70 controls matched on age and gender). Participants provided blood samples in which we measured biomarkers of exposure to several polybrominated diphenyl ethers (PBDE) FRs. Because levels of FRs in household dust are strongly correlated with personal exposure, we visited participants’ homes and collected dust samples for the assessment of additional types of FRs. Participant demographic and clinical information was collected via questionnaire, and tumor histology data were abstracted from medical records.

Results: Reflecting known gender differences in PTC risk, our final study population was 78.6% female. Overall, participants averaged 48 years of age and cases and controls were similar with respect to race and ethnicity, household income, and health history.  Our results suggest that higher levels of some FRs, particularly decabromodiphenyl ether (BDE-209) and tris(2-chloroethyl) phosphate (TCEP) in dust, are associated with increased odds of developing PTC. Those with dust BDE-209 concentrations above the median were 2.29 times as likely to have PTC [95% confidence interval (95% CI): 1.03, 5.08] compared to those with low BDE-209. Associations with PTC differed by the presence or absence of the BRAF V600E mutation and measures of tumor aggressiveness. For example, those with the highest levels of BDE-209 in the dust were 14.2 times as likely to have BRAF negative (95% CI: 1.63, 123) and less aggressive tumors (i.e. small tumors without extra-thyroidal extension). TCEP, in contrast, was more strongly associated with larger, more aggressive tumors. For example, participants with house dust TCEP levels above the median were 4.14 times likely to have PTC with extra-thyroidal extension (95% CI: 1.01, 16.98), but were not significantly more likely to have PTC without extra-thyroidal extension (OR=2.13; 95% CI: 0.89, 5.07).

Conclusions: Taken together, our results suggest exposure to several FRs may be associated with the occurrence and severity of PTC.

 

Disclosure: JAS: Member, Data Monitoring Committee, Medullary Thyroid Cancer Consortium Registry, Novo Nordisk, Astra Zeneca, GlaxoSmithKline, Eli Lilly. Nothing to Disclose: KH, AL, CMB, HS